The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Typically, when an engine is operating, both air and fuel are supplied to a combustion chamber of a cylinder. Fuel is injected by an injector, while air is supplied to the combustion chamber through the operation of a cam and a valve provided in the cylinder head. At this time, it is required to adjust a point in time to open the valve or the amount of the opening of the valve depending on the operation area of the engine. In order to blow air taken in by the cam and the valve into the combustion chamber, the valve disposed on the upper surface of the combustion chamber is opened and closed by the cam using a hydraulic circuit.
FIG. 1 illustrates a valve opening and closing apparatus of the related art. The valve opening and closing apparatus controls a point in time to open a valve 10 using a cam 20 and the amount of the opening of the valve 10 using a hydraulic circuit. We have discovered that since the hydraulic circuit is composed of a plurality of parts, such as a pump unit 30, a high-pressure chamber 40, an accumulator 50, a deaerator 60, a pressure chamber 70, a check valve 80, a solenoid valve 90, and a brake unit 95, the hydraulic circuit increases the complexity, weight, and cost of the valve opening and closing apparatus. In addition, when a pressure-forming closed circuit has a large volume, the response of a hydraulic system becomes slow, degrading performance.
In addition, when the response of the hydraulic system is delayed, jumping occurs, i.e. a nose 21 of the cam is instantaneously separated from the pump unit 30 (or a rocker arm). In this case, accumulated impact fatigue causes an endurance problem, such as cam-fitting or damage to the pump unit 30.
Therefore, we have discovered that a valve opening and closing apparatus having a simplified configuration and a superior response rate, able to adjust the point in time to open a valve and the amount of the opening of the valve by means of cams, is required. This apparatus is also required to enable the cams to stay in continuous contact with contact members while rotating.